Marsupials are all the members of the infraclass Marsupialia which diverged from the main radiation of placental mammals around 130–160 mya. They exhibit a myriad of adaptations to different habitats, wide array of diet, locomotor modes, and social and mating systems. Even though their point of origin is contested, the earliest metatherian fossil record (comprising marsupials and their closest fossil relatives) has been discovered in Asia and dated to the Early Cretaceous (stretching from 146 Ma and 100 Ma). The earliest common ancestor of eutherians (modern placentals) and metatherians is thought to be Juramaia sinensis. Dated back to the Jurassic (160 Ma) and discovered in China, it exhibits scansorial (adapted for climbing) forelimb anatomy, weights around 15–17 g, and based on tooth morphology, was an insectivore. It is more closely related to most modern day placentals than all metatherians including the earliest known Sinodelphys and Deltatheridium.
- Kelava, I., Lewitus, E., & Huttner, W. B. (2013). The secondary loss of gyrencephaly as an example of evolutionary phenotypical reversal. Frontiers in Neuroanatomy, 7(16). https://doi.org/10.3389/fnana.2013.00016.
- Papini, M. R., Mustaca, A. E., Tiscornia, G., & DiTella, M. (1987). Context learning in the marsupial (Lutreolina crassicaudata Red Opossum). International Journal of Comparative Psychology, 1(2). https://escholarship.org/uc/item/9sk6x0sx.
- Suárez, R., Paolino, A., Fenlon, L. R., Morcom, L. R., Kozulin, P., Kurniawan, N. D., & Richards, L. J. (2018). A pan-mammalian map of interhemispheric brain connections predates the evolution of the corpus callosum. Proceedings of the National Academy of Sciences, 115(38), 9622–9627. https://doi.org/10.1073/pnas.1808262115.CrossRefGoogle Scholar